Thermolysis of alkoxy disilanes in the presence of alcohols to provide hydrogen-substituted alkoxymonosilanes



United States Patent THERMOLYSIS 0F ALKOXY DISILANES IN THE PRESENCE OFALCOHOLS TO PROVIDE HYDRO- GEN-SUBSTITUTED ALKOXYMONOSILANES William H.Atwell, Midland, Mich., assignor to Dow Corning Corporation, Midland,Mich., a corporation of Michigan No Drawing. Filed Sept. 18, 1967, Ser.No. 668,652

Int. Cl. C07f 7/18; C09k 3/18 US. Cl. Mil-448.8 5 Claims ABSTRACT OF THEDISCLOSURE Hydrogen-substituted alkoxymonosilanes are produced byheating alkoxy-containing disilanes at a preferred temperature of from175 C. to 225 C. under neutral conditions and in the presence of analcohol. Illustrative of the above process is the following:

200 0. CH3OSl-SiOCH3 CHaOH (CHQ SKOCHa) (CHQaSiHOCH:

The resulting alkoxymonosilanes, and particularly thehydrogen-substituted alkoxymonosilane, are useful as water repellentsand can be employed as precursors in the production of other usefulmaterials.

This invention relates to a process for producing hydrogen-substitutedalkoxymonosilanes which comprlses heating under neutral conditions, adisilane of the formula (B0)]; i-Si(OR)n in which,

R is a lower alkyl radical containing from 1 to 6 carbon atomsinclusive, and n has a value of from 1 to 3 inelusive,

in the presence of an alcohol of the formula ROH, in which R is a loweralkyl radical containing from 1 to 6 carbon atoms inclusive, thereafterrecovering the desired hydrogen-substituted alkoxymonosilane.

As noted above, R can be any lower alkyl radical containing from 1 to 6carbon atoms inclusive such as the methyl, ethyl, propyl, isopropyl,butyl, t-butyl, amyl, and hexyl radical. However, for purposes of thepresent invention, the methyl radical is to be preferred. For thisreason, the obviously preferred alcohol is methanol, although ethanol,propanol, isopropanol, and butanol can be used. A temperature range offrom 175 C. to 225 C. is to be preferred. The minimum temperature is notcritical, however, for practical considerations and the like, thetemperature must be sufiicient, i.e., 175 C., so that the reaction willproceed at a feasible rate. If temperatures in excess of 225 C. areemployed, undesirable side reactions may occur due to the redistributionof Si--H bonds and Si-OR bonds.

The fact that the process must be conducted under neutral conditions isto a certain extent critical. The term neutral conditions" merelyimplies that there cannot be significant amounts ofacid or alkalipresent. For example, if a significant amount of alkali is present itwould initiate a redistribution of Si-Si bonds that would result indetrimental effects. However, it is of importance to note that traces ofalkalinity which might be caused by the alkalinity of the glassapparatus in which the process is performed is not sufiicientlysignificant to be deleterious.

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Also, if a significant amount of acid is present, the alkoxy radical maybe condensed; however, minor amounts of acids such as chlorosilanes canbe tolerated as long as the acid is anhydrous and is not a catalyst forside reactions, i.e., the redistribution of Si-CH bonds.

The process of the present invention must be conducted under essentiallyanhydrous conditions to prevent hydrolysis of the SiOR bond. Bothpressure and reaction time do not appear to be particularly critical.

Due to the nature of the thermal decomposition of the starting material(the alkoxy-containing disilanes), the formation of alkoxymonosilanes asWell as the desired hydrogen-substituted alkoxymonosilanes occurs. Itshould be noted, however, that excessive reaction times are not desiredsince the yield of the hydrogen-substituted alkoxymonosilanes willdecrease as the disilane is proportionately consumed. Thehydrogen-substituted alkoxymonosilane is subsequently isolated by wellknown means, i.e., by standard distillation and the like.

The hydrogen-substituted alkoxymonosilane which is obtained is aparticularly useful compound. Illustrative of the numerous uses to whichthe silane can be put is as a water repellent or as a precursor toproduce other useful materials.

The following examples are merely illustrative and are not intended tolimit the invention which is properly delineated in the appended claims.

EXAMPLE 1 Methanol and (CH O) SiSi(OCH were mixed in a 1.5: 1.0 moleratio and heated in a closed system at a temperature of 200 C. Thepercent yield of SiH(OCH vs. the percent conversion of (CH O) SiSi(OCHwere determined periodically by quantitative gas-liquid-chromatographyand the following results were obtained.

Yield (CH30)3SlH, Conversi Time (hrs.) percent (CHaO)eSiz, perce h l;

EXAMPLE 2 The above procedure was repeated with the exception that adisilane of the formula (0 H O )gSi-SKO C H was employed. The followingresults were obtained.

Yield Conversion OH3HS1 OCH CHO Si. CH 'Inne (hrs.) perce zi t pr e ntEXAMPLE 3 The above procedure was repeated with the exception that adisilane of the formula C1130 Si-SiO 0 H3 was employed. The followingresults were obtained.

(cHahHslo g (cfisofz s l l fiig Time (hrs.) percent percent 3 EXAMPLE 4Substantially equivalent results were obtained when the reaction wasconducted at a temperature of 225 C.

EXAMPLE 5 Substantially equivalent results were obtained when thealcohol employed was ethanol, propanol, isopropanol, or butanol.

That which is claimed is:

1. A process for producing hydrogen-substituted alkoxymonosilanes whichcomprises heating under neutral conditions, a disilane of the formula 2.The. process of claiml in. which the temperature is within the range offrom C. to 225 C.

3. The process as recited in claim 1 in which the temperature is 200 C.

4. The process of claim 3 in which the disilane has the formula r (CHOhSi-SKO CH3);

5. The process of claim 4 in which the alcohol is methanol.

7 References Cited UNITED STATES PATENTS 4/1959 7 Kuriyagawa et al.260-4483 6/1958 George et a1. 260-448.8

OTHER REFERENCES TOBIAS E. LEOW, Primary Examiner P. F. SHAVER,Assistant Examiner US. Cl. X.R. 106-43

